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mgcp: Parse SDP to get rate and packet duration 

This patch parses the 'ptime' and 'maxptime' SDP attributes, and the
SDP rate information and sets up packet_duration_ms accordingly. If
the packet duration is unknown or allows for different values (e.g.
because 'ptime' uses a range or 'maxptime' allows for more than one
frame) the duration is set to 0.

Sponsored-by: On-Waves ehf
This commit is contained in:
Jacob Erlbeck 2013-12-10 13:09:37 +01:00 committed by Holger Hans Peter Freyther
parent 2c2ca4df38
commit 24754f0490
3 changed files with 61 additions and 11 deletions
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9
openbsc/src/libmgcp/mgcp_network.c
View File

@ -300,6 +300,15 @@ void mgcp_patch_and_count(struct mgcp_endpoint *endp, struct mgcp_rtp_state *sta
state->seq_offset, state->packet_duration,
inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
endp->conn_mode);
if (state->packet_duration == 0 && rtp_end->force_constant_timing)
LOGP(DMGCP, LOGL_ERROR,
"Cannot patch timestamps on 0x%x: "
"RTP packet duration is unknown, SSRC: %u, "
"from %s:%d in %d\n",
ENDPOINT_NUMBER(endp), state->in_stream.ssrc,
inet_ntoa(addr->sin_addr), ntohs(addr->sin_port),
endp->conn_mode);
} else if (state->in_stream.ssrc != ssrc) {
LOGP(DMGCP, LOGL_NOTICE,
"The SSRC changed on 0x%x: %u -> %u "

53
openbsc/src/libmgcp/mgcp_protocol.c
View File

@ -562,25 +562,64 @@ static int parse_sdp_data(struct mgcp_rtp_end *rtp, struct mgcp_parse_data *p)
{
char *line;
int found_media = 0;
int audio_payload = -1;
for_each_line(line, p->save) {
switch (line[0]) {
case 'a':
case 'o':
case 's':
case 't':
case 'v':
/* skip these SDP attributes */
break;
case 'a': {
int payload;
int rate;
int channels = 1;
int ptime, ptime2 = 0;
char audio_name[64];
char audio_codec[64];
if (audio_payload == -1)
break;
if (sscanf(line, "a=rtpmap:%d %64s",
&payload, audio_name) == 2) {
if (payload != audio_payload)
break;
if (sscanf(audio_name, "%[^/]/%d/%d",
audio_codec, &rate, &channels) < 2)
break;
rtp->rate = rate;
if (channels != 1)
LOGP(DMGCP, LOGL_NOTICE,
"Channels != 1 in SDP: '%s' on 0x%x\n",
line, ENDPOINT_NUMBER(p->endp));
} else if (sscanf(line, "a=ptime:%d-%d",
&ptime, &ptime2) >= 1) {
if (ptime2 > 0 && ptime2 != ptime)
rtp->packet_duration_ms = 0;
else
rtp->packet_duration_ms = ptime;
} else if (sscanf(line, "a=maxptime:%d", &ptime2) == 1) {
if (ptime2 * rtp->frame_duration_den >
rtp->frame_duration_num * 1500)
/* more than 1 frame */
rtp->packet_duration_ms = 0;
}
break;
}
case 'm': {
int port;
int payload;
audio_payload = -1;
if (sscanf(line, "m=audio %d RTP/AVP %d",
&port, &payload) == 2) {
&port, &audio_payload) == 2) {
rtp->rtp_port = htons(port);
rtp->rtcp_port = htons(port + 1);
rtp->payload_type = payload;
rtp->payload_type = audio_payload;
found_media = 1;
}
break;
@ -608,8 +647,10 @@ static int parse_sdp_data(struct mgcp_rtp_end *rtp, struct mgcp_parse_data *p)
if (found_media)
LOGP(DMGCP, LOGL_NOTICE,
"Got media info via SDP: port %d, payload %d, addr %s\n",
ntohs(rtp->rtp_port), rtp->payload_type, inet_ntoa(rtp->addr));
"Got media info via SDP: port %d, payload %d, "
"duration %d, addr %s\n",
ntohs(rtp->rtp_port), rtp->payload_type,
rtp->packet_duration_ms, inet_ntoa(rtp->addr));
return found_media;
}

10
openbsc/tests/mgcp/mgcp_test.ok
View File

@ -16,22 +16,22 @@ Testing AUEP2
Testing MDCX1
Testing MDCX2
Testing CRCX
Packet duration not set
Detected packet duration: 40
Requested packetetization period: 20-20
Testing MDCX3
Packet duration not set
Requested packetization period not set
Testing MDCX4
Packet duration not set
Detected packet duration: 40
Requested packetetization period: 20-20
Testing MDCX4_PT1
Packet duration not set
Detected packet duration: 40
Requested packetetization period: 20-40
Testing MDCX4_PT2
Packet duration not set
Detected packet duration: 40
Requested packetetization period: 20-20
Testing MDCX4_PT3
Packet duration not set
Detected packet duration: 40
Requested packetization period not set
Testing DLCX
Detected packet duration: 20